ING Bank has released its Zero-Knowledge Range Proof (ZKRP) solution at the inaugural Enterprise Ethereum Alliance Event in Amsterdam.

A zero-knowledge proof (ZKP) is a cryptographic method that allows a party (the prover) to prove to another party (the verifier) that a given statement is true, without conveying any additional information. For example, a ZKP allows you to proof that you're of a certain age, without revealing your actual age.

Zero-Knowledge Range Proofs (ZKRP) allow for proofing that a number lies within a certain range. For example, a mortgage applicant could prove that their salary sits within a certain range, without revealing the exact figure. Similarly, it could prove that a payment amount is within a limit, but it does not show the exact amount.

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This is a new and burgeoning area of mathematics and computer science with particular relevance to blockchains, privacy and so on. The ZKRP solution, which has been internally developed by the ING blockchain team, provides a less computationally heavy version of generic zero knowledge proofs (the best known of these are zk-SNARKs).

When the bank benchmarked its ZKRP implementation against several available functions, it found the implementation is a factor 10 more efficient then the zk-SNARKs solution currently used in Ethereum's test network. This efficiency is particularly important in a blockchain context where all nodes need to verify all transactions, which is why ING has developed and implemented a specific ZKP that can verify a range proof.

The ZKRP holds the same three properties as ZKP, which are completeness, soundness and zero-knowledge, according to an ING white paper.

ING has launched ZKRP as an open source solution, which means that other interested parties in the development community are able to download, access and even contribute to the solution, which allows for greater testing and can lead to improvements.

Mariana Gomez de la Villa, global head of ING's blockchain programme, said: "Until recently, one of the primary challenges for applying distributed ledger technology in the banking sector was ensuring that data privacy was protected while simultaneously meeting regulatory reporting requirements.

"While ZKP technology has provided us with a way of overcoming that, the main limiting factor is the resource and therefore cost that each verification would generate. However, ING's ZKRP solution has been proven to be ten times more efficient than other ZKPs in the ethereum test network, while upholding the same three principles: completeness, soundness and zero-knowledge."